MPG From CdRom

I need to be able to find the cd rom drive letter from my app. and plug it into my code:

Private Sub Command1_Click()
MediaPlayer1.FileName = "WMT.MPG"
End Sub

So i can install my app. but run my MPG's from the system's cd rom

I don't want to just put in D: because it'll run on numerous different systems which may have different drive letters for the cd rom

any ideas?????